Transformational catalytic performance in rate and selectivity is obtainable through catalysts that change on the time scale of catalytic turnover frequency. In this work, dynamic catalysts are defined in the context and history of forced and passive dynamic chemical systems, with classification of unique catalyst behaviors based on temporally-relevant linear scaling parameters. The conditions leading to catalytic rate and selectivity enhancement are described as modifying the local electronic or steric environment of the active site to independently accelerate sequential elementary steps of an overall catalytic cycle. These concepts are related to physical systems and devices that stimulate a catalyst using light, vibrations, strain, and electronic manipulations including electrocatalysis, back-gating of catalyst surfaces, and introduction of surface electric fields via solid electrolytes and ferroelectrics. These catalytic stimuli are then compared for capability to improve catalysis across some of the most important chemical challenges for energy, materials, and sustainability. File list (2) download file view on ChemRxiv Perspective_Manuscript_ChemRxiv.pdf (3.88 MiB) download file view on ChemRxiv Perspective_Supporting_Information_ChemRxiv.pdf (149.75 KiB)

It is a truth universally acknowledged that faster catalysts enable more efficient transformation of molecules to useful products and enhance the utilization of natural resources. However, the limit of static catalyst performance defined by the Sabatier principle has motivated a dynamic approach to catalyst design, whereby catalysts oscillate between varying energetic states. In this work, the concept of dynamic catalytic resonance was experimentally demonstrated via the electrocatalytic oxidation of formic acid over Pt. Oscillation of the electrodynamic potential between 0 and 0.8 V NHE via a square waveform at varying frequency (10 −3 < f < 10 3 Hz) increased the turnover frequency to ∼20 s −1 at 100 Hz, over one order of magnitude (20×) faster than optimal potentiostatic conditions. We attribute the accelerated dynamic catalysis to nonfaradaic formic acid dehydration to surface-bound carbon monoxide at low potentials, followed by surface oxidation and desorption to carbon dioxide at high potentials.

Transformational catalytic performance in rate and selectivity is obtainable through catalysts that change on the time scale of catalytic turnover frequency. In this work, dynamic catalysts are defined in the context and history of forced and passive dynamic chemical systems, with classification of unique catalyst behaviors based on temporally-relevant linear scaling parameters. The conditions leading to catalytic rate and selectivity enhancement are described as modifying the local electronic or steric environment of the active site to independently accelerate sequential elementary steps of an overall catalytic cycle. These concepts are related to physical systems and devices that stimulate a catalyst using light, vibrations, strain, and electronic manipulations including electrocatalysis, back-gating of catalyst surfaces, and introduction of surface electric fields via solid electrolytes and ferroelectrics. These catalytic stimuli are then compared for capability to improve catalysis across some of the most important chemical challenges for energy, materials, and sustainability.

It is a truth universally acknowledged that faster catalysts enable the more efficient transformation of molecules to useful products and enhance the sustainable utilization of natural resources. However, the limit of <i>static</i> catalyst performance defined by the Sabatier principle has motivated a new approach to <i>dynamic</i> catalyst design, whereby catalysts oscillate with time between varying energetic states at sufficiently high resonant frequencies to overcome the Sabatier ‘volcano peak’. In this work, the concept of dynamic catalytic resonance was experimentally demonstrated via the electro-catalytic oxidation of formic acid in water on a Pt working electrode within a semi-continuous multi-phase flow reactor. Steady-state electro-oxidation of formic acid at 0.6 V (NHE) exhibited a maximum turnover frequency (TOF) of CO₂ formation of ~1.0 s^-1 at room temperature. However, oscillation of the electrodynamic potential between 0.8 V and open circuit via a square waveform at varying frequency (10^-3 < <i>f</i> < 10³ Hz) increased the optimal TOF to ~5 s^-1 at 0.5 Hz. An even higher TOF of ~20 s^-1 was observed at a resonant frequency of 100 Hz for a square waveform oscillating between zero and 0.8 V. The rate increase in formic acid electro-oxidation via catalytic resonance of more than an order of magnitude (20x) above potentiostatic conditions was interpreted to occur by non-faradaic formic acid dehydration to surface-bound carbon monoxide at low potentials, followed by surface oxidation and desorption to carbon dioxide at high potentials.

This manuscript summarizes observations made during the conversion of propanoic acid over Pt/SiO 2 under H 2 -rich environments. Under these conditions, Pt is active for hydrogenation and hydrodeoxygenation, which leads to the formation of propionaldehyde, 1-propanol, and propane. Pt also facilitates decarbonylation of propanoic acid and propionaldehyde, which forms ethane and CO. The accumulation of CO with increasing residence time poisons the Pt catalyst and makes it difficult to achieve high propanoic acid conversions on practical time scales. During the conversion of propanoic acid on Pt/ SiO 2 , sequential reactions play a critical role in determining product distributions. We resolve their contributions through analysis of rates and selectivities during the conversion of propanoic acid, propionaldehyde, 1-propanol, CO, and CO 2 in various environments. We conclude that the main challenge facing the selective production of partial hydrodeoxygenation productsnamely propionaldehyde and 1-propanolis that one must facilitate dehydroxylation of propanoic acid while avoiding thermodynamically favorable decarbonylation and alcohol hydrogenolysis pathways. Because these side reactions are effectively irreversible under hydrodeoxygenation conditions, this can only be accomplished by suppressing rates of decarbonylation and 1-propanol hydrogenolysis. We reconcile macroscopic trends with a reaction mechanism that includes parallel and sequential reactions occurring during the hydrodeoxygenation of propanoic acid over Pt/SiO 2 .